The fermentation of carbohydrates to form butanol and acetone by Clostridium acetobutylicum (hereafter abbreviated C. acetobutylicum) was disclosed by Weizmann in U.S. Pat. No. 1,315,585. For many years, this process was used for the preparation of acetone and butanol, and a certain amount of ethyl alcohol was obtained as a by-product.
Eventually, the microbial process was displaced by chemical processes which provide the same products using cheap fossil fuel row materials. However, the gradual depletion of petroleum fossil fuel with the resultant increase in prices of petrochemical feedstocks has revived interest in this fermentation reaction that uses carbohydrates, which are renewable raw materials.
One problem encountered in production of butanol by the fermentation process is the long time before the microorganism begins to produce appreciable quantities of solvent. This is particularly true if attempts are made to run the reaction in a continuous fermentor. It would therefore be of considerable interest if a strain of microorganism could be developed which would give accelerated batch fermentations or which would reduce the time necessary for the establishment of a steady state of solvent production in a continuous fermentation.
Previous workers have believed that the sporulation of C. acetobutylicum is necessary to maintain the organism in an active solvent-producing state. See, for example, Bahl, et al, European J. Appl. Microbiol. Biotechnol., 14, 17-20 (1982). Recently, Jones, et al, Applied and Environmental Microbiology, 43, 1434-1439 (1982), reported that certain asporogenic mutants of C. acetobutylicum would produce solvents. However, these must be mutants that are still active producers of clostridial forms of cells.
A strain of C. acetobutylicum has now been developed which is a good producer of butanol even though it shows little tendency to form spores or to change to clostridial forms. Furthermore, this strain generates butyl alcohol at an accelerated rate in a batch fermentation and reaches a steady state of solvent production in a continuous fermentation in a much shorter time than does the parent strain.